(Just to clarify, I don’t pretend to follow all my own rules! I’m still learning to do that…)
‘Head-hopping’ is the name many writers give to the act of switching between different characters. I like to think of it visually as moving the fictional camera from behind one character’s eyes to behind another’s. This crops up a lot in collaborations, which isn’t so bad, because they’re good practice, but rarely go much further, and in third person omniscient, which I find a lot in the traditional classics. In many cases the character’s thoughts are included in the perspective (a POV can be in first or third person–or second, indeed).
Now, head-hopping is something I wouldn’t advise for a real MS, because as a reader, I get irritated when I know the exact thoughts of every character, and as a writer it takes a good deal of deliberation to create a unique style of thought process for each character. Exactly what you don’t want is readers finding the characters perceive events either too similarly or in cliché. They just blend together, and readers begin to wonder subconsciously whether the writer is really as narrow-minded as he or she seems.
So it’s personal to me, and very wise and wonderful authors can make it work, but I wouldn’t go in for head-hopping. Stick to one or two characters and go into depth; the minor characters can look after themselves, and the reader will probably appreciate it if you allow them to contrive their own elucidations of SCs, too.
And even if readers don’t do that, mystery builds tension. Keep them in ignorance of the inner workings of your characters’ minds! (This runs perilously over into the ‘show not tell’ debate, I am aware. But it all links together, you will see.)
MCs, I’ve noticed, are rarely the favourites, but the SCs come in for much more vigorous devotion. Possibly this is due to the fact that readers can interpret the SCs for themselves, and there may be one particular character they imagine they can relate to, simply because of their interpretation. I always find it interesting which characters different readers naturally drift towards—it can be very illuminating, and often unexpected(!).
Head-hopping is the equivalent of spoon-feeding: don’t do this, if you’re aiming for an intelligent audience.
Yes; it’s a trap many of the more ambitious writers fall into. We have so much to tell our readers, and we know all we have to tell is dreadfully interesting. But we forget that we also profess to appeal to an audience of intellectual young people who will appreciate our writing for the masterwork it is: and therefore our audience is just as intelligent as we are, and can draw generally pretty accurate conclusions from just a little that we write.
‘Less is more’…‘quality not quantity’… I used to despise these sayings. I wanted to write at length. I wanted to write everything in my mind and more besides, going off on a tangent at every turn. But writing must be concise if it is to deeply entertain one’s readers.
It’s not just ‘create, create, create! Ah, it’s wonderful, and so am I; I must now show all the world how wonderful I am’. Writing is a deeply rational process, especially when it comes to planning and editing. Bypassing either of these essential stages (unless you’re a creative genius, which, I can assure you, however much you insist ‘but I’m different to everyone else’, you’re not) is the death to your masterpiece.
Anyway, I am truly going off on a tangent, now, contrary to my own advice! In short, if you’re going to go in for head-hopping, think it over seriously.